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International Journal of Bioprinting Bioprinting hearing loss treatment

3D printing, the study failed to provide functional data achieved in the utilization of novel materials for addressing
following the implantation procedure. Sinkkonen et al. hearing impairment. Our previous research endeavors
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employed a liquid photosensitive polymer, Clear V4, in the have investigated the efficacy of tissue engineering
process of 3D printing to fabricate an artificial ossicular methodologies in promoting the differentiation of inner
chain, which was subsequently evaluated using micro- ear stem cells into hair cells, along with their targeted
CT imaging. The findings of the study suggested that the delivery and integration. Nevertheless, concerns regarding
performance metrics of accuracy, acoustic functionality, safety, efficacy, and functionality persist, underscoring the
and ease of implantation of the artificial ossicular chain necessity for continued enhancements.
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were comparable, if not superior, to those of conventional
commercial titanium partial ossicular replacement Bioprinting emerges as a viable strategy for augmenting
prostheses. 64,65 Table 1 compares the 3D-printed prosthesis the proliferation and specialization of stem cells within
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and commercial titanium prosthesis for OCR. the inner ear. Milica et al. demonstrated the successful
fabrication of complex structures, including the cochlea
Nevertheless, the current constraints imposed and glomeruli, utilizing a novel high-throughput
by material properties limit the applicability of these omnidirectional printing technique and polymeric
3D-printed artificial ossicular chains solely to surgical elastomers. This was followed by the generation of
training purposes, precluding their direct implantation vascularized tissues through the seeding of parenchymal
within the human body. It is currently possible to fabricate cells, enabling the achievement of microtubule bioprinting
cartilage and bone structures using 3D bioprinting, but at the millimeter scale. In a related study, Huang et
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studies about OCR were historically scarce. This is mainly al. developed a bionic cochlea through the utilization
because the ossicular chain is too small to shape perfectly, of 3D bioprinting technology, enabling investigations
while existing prostheses are well established. However, into cochlear implant signaling and patient condition
there is substantial room for improvement, like the assessments that were previously unattainable within the
preparation of bioinks with improved printability. 66 confines of the human inner ear. Li et al. conducted
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a study in which inner ear stem cells were cultured in a
3. Bioprinting applications in sensorineural 3D matrix utilizing gelatin methacryloyl/sodium alginate
hearing loss (GelMA/SA) scaffolds. These stem cells, derived from
Sensorineural deafness is a condition resulting from the organ of Corti in neonatal mice, were utilized to
injury to the organ of Corti hair cells, auditory nerve, produce bioink. Subsequently, the researchers utilized
auditory center conduction pathways, or various levels of 3D bioprinting methods to fabricate a Corti organoid,
the auditory center. This type of hearing impairment is which features notable improvements in the proliferation
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often caused by factors such as noise exposure, infections, and specialization of the inner ear stem cells, potentially
ototoxic medications, aging, and genetic predispositions. due to the suppression of Notch signaling. Subsequent
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Our prior studies have investigated the impact of investigations using the Corti organoid model
epigenetics on the growth, viability, and restoration demonstrated structural characteristics comparable to the
of inner ear cells, emphasizing its essential function native organ of Corti. Additionally, there were no significant
in preserving auditory function. While hair cells can disparities in hair cell quantity and morphology between
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regenerate in fish and birds, the lack of regenerative ability the experimental and control cohorts. Furthermore, these
in mammals presents a considerable obstacle in addressing inquiries delved into the repercussions of coptisine- and
sensorineural deafness. Recent developments have been neomycin-induced impairment on hair cells through
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Table 1. Comparison between 3D-printed prosthesis and commercial titanium prosthesis for OCR

Indices 3D-printed prosthesis Commercial titanium prosthesis
Surgical maneuverability Stiffer and less flexible Good flexibility
Acoustical performance 9 dB in PTA reduction 8 dB in PTA reduction
Major constituent Liquid photopolymer Titanium
Difficulty of implantation Acceptable Convenient
Material cost Inexpensive Costly
Application range Surgical training Clinical practice
Abbreviations: OCR: ossicular chain reconstruction; PTA: pure tone audiometry

Volume 10 Issue 4 (2024) 110 doi: 10.36922/ijb.3497